As the solid-state imaging devices for compact digital cameras and mobile cameras, back-illuminated solid-state imaging devices (BSIs) have been developed to improve the sensitivity and the shading characteristics of fine pixels (see Patent Document 1, for example).
A BSI can be employed as a solid-state imaging device for a digital still camera that takes images of APS, 35 mm, or type 1 in size. However, such a digital still camera has a sufficiently large pixel size (1.980 μm or larger, for example), and therefore, has low cost-effectiveness. For this reason, introduction of BSIs was delayed. However, even such a digital still camera is expected to capture high-sensitivity, high-definition images these days, and introduction of BSIs is being considered.
A BSI can have photodiodes with a larger area than in a front-illuminated solid-state imaging device (FSI). Furthermore, any multilayer metal interconnect is not provided on the light entering side, and accordingly, incident light can be efficiently taken into photodiodes. As a result, sensitivity characteristics are improved.
On the other hand, since the area of each photodiode is large, and any multilayer metal interconnect is provided on the light entering side, the photodiodes capture too much reflection light from a sealing glass surface, an infrared cut filter (IRCF), an optical system, and the like, which are provided on the illuminated side of the microlenses. As a result, flare, ghosts, and color mixing easily occur, and degrade the quality of captured images.
In a suggested measure against the above, two inorganic films are provided as antireflection films on the surfaces of the microlenses, to prevent occurrences of flare, ghosts, color mixing, and the like (Patent Document 2, for example).